1. Field of the Invention
The present invention relates to crash survivable protective enclosures for flight recorders used in aircraft and other vehicles operating over land and water. More particularly, the invention is directed toward a crash survivable enclosure which is capable of withstanding high impact, shock and mechanical penetration forces that commonly occur in a crash and the high temperatures, flames and heat that often develop after a crash. In addition, the enclosure is specially designed for resisting damage to solid state memory devices contained therein, even if the enclosure is subjected to immersion in fresh water or salt water for a prolonged period.
2. Description of the Prior Art
Solid state memory devices have been used in flight recorders for recording essential flight data or information useful in determining causes of crashes or other mishaps in aircraft and other vehicles. When a crash occurs, it is essential that the recorded information on board survive the crash and subsequent events including heat, cold, flame and fire that may afterwards ensue. In addition, should the crash or impact occur over the ocean or another body of water, it is essential that the crash survivable portion of the flight data recorder remain intact for a prolonged period of time, even though the enclosure is submerged to a substantial depth in sea water or fresh water until the recorder is eventually located and retrieved for examination of the data contained in the solid state memory devices thereof.
U.S. Pat. No. 4,694,119 discloses a solid state memory contained in a small crash protective container. The device is encapsulated in a heat sink formed of a synthetic amide wax designed to change phase at a temperature below the maximum acceptable temperature of the memory device to thereby protect the solid state memory or other solid state devices from damage due to heat and fire.
U.S. Pat. No. 4,944,401 also discloses a solid state memory device carried in a crash survivable protective enclosure and encapsulated in a synthetic wax having a relatively high heat of fusion so as to provide a heat sink for the protection of the solid state memory device contained in the protective enclosure.
U.S. Pat. No. 5,123,538 discloses a similar devices having an inner enclosure that acts as a sacrificial anode to protect an electronic device from salt water. A plastic or rubber conformal coating surrounds the device contained in the inner enclosure.